1. Field of the Invention
The present invention relates to a novel azo compound which is useful as an azo dye, a colored curable composition which is suitable for forming a color filter for use in a liquid crystal display (LCD) or a solid-state image sensor (such as a CCD and CMOS), a color filter utilizing such colored curable composition, and a manufacturing method therefor.
2. Description of the Related Art
Conventionally, azo dyes, showing optical absorption in various visible regions, have been utilized in various fields as dyes. Azo dyes have been utilized in various fields, such as a colorant for synthetic resin, a printing ink, a dye for a sublimation-type heat transfer material, an inkjet ink, and a dye for a color filter. One of the major performances required for an azo dye as a dye is an absorption spectrum. A color hue of a dye gives a significant influence on the color, texture, or the like of an article colored with such dye, and provides a significant visual effect. Consequently, the absorption spectra of dyes have been researched for many years. An outline is shown in J. Fabian and H. Hartmann “Light Absorption of Organic Colorants” (Springer-Verlag, Berlin, 1980), and the detailed description is shown in Heinrich Zollinger “Color Chemistry” (Weinheim, New York, Basel, Cambridge) and Hiroshi Noguchi “Gosei Senryo” (Sankyo Shuppan, 1970), respectively in the chapters for azo dyes or azo pigments.
Recently, color images have become the main stream as image recording materials, and applications of dyes have been more diversified. Specifically, dyes are frequently employed in an ink jet-type recording material, a thermal transfer-type recording material, an electrophotographic recording material, a transfer-type silver halide photosensitive material, a printing ink, and the like. Moreover, color filters are utilized for recording or reproducing a color image, in an imager such as a CCD for use in image pickup equipment, and in displays such as an LCD or a PDP. Furthermore, dyes are also utilized for coloring matters and hair dying. In these color image recording material or color filters, there are employed colorants (dyes or pigment) of three primary colors in so-called an additive or subtractive color mixing method, in order to reproduce or record a full-color image. However, at present, there is no colorant having; an absorption characteristic capable of realizing a preferred color reproduction range, capable of withstanding various conditions of use and environmental conditions, and having satisfactory color hues and satisfactory resistances. Improvements are therefore being strongly desired.
These colorants used in such respective applications are commonly required to have a preferable absorption characteristic in terms of color reproduction, resistance under environmental conditions where they are used, and a large molar absorption coefficient.
Conventionally, azo dyes having a nitrogen-containing 5-membered ring as an azo component have been disclosed in Japanese Patent Application Laid-Open (JP-A) No. 55-161856, Japanese Patent Application Laid-Open No. 6-145543, Japanese Patent Application Laid-Open No. 7-224230, Japanese Patent Application Laid-Open No. 9-234964, Japanese Patent Application Laid-Open No. 9-277703, and Japanese Patent Application Laid-Open No. 2003-246942. However, they are not satisfactory in terms of color hue, resistance, and molar absorption coefficient. Moreover a method of synthesizing a 5-membered heterocyclic azo dye is disclosed in the Journal of Heterocyclic Chemistry, Vol. 22, pp. 813-816 (1985) but this does not provide an azo dye satisfactory in terms of color hue, spectral absorption coefficient, and the like.
As a color filter to be formed on a device for realizing a color structure in a solid-state image sensor or a liquid crystal display, there is known a color filter comprising a yellow filter layer, a magenta filter layer, and a cyan filter layer, and a color filter comprising a red filter layer, a green filter layer, and a blue filter layer, in which such filter layers are formed in an adjacent manner in the same plane on a substrate. In these filter layers are formed a striped pattern or a mosaic pattern. As a manufacturing method of a color filter, there have been proposed various methods. Among these, a so-called color resist method is widely practiced, in which a patterning step for exposing and developing a dye-containing a photosensitive resinous composition, is repeated for a necessary number of times.
The color resist method is a method (hereunder, also called “pigment dispersion method”) of producing a color filter by a photolithographic method utilizing colored radiation-sensitive compositions in which pigments are dispersed in various photosensitive compositions. This method is suitable for producing a color filter for a color display of a large size or a high definition, since it can provide high stability against light and heat because of the use of pigments, and it can provide a sufficient positional precision by photolithographic patterning.
In order to produce a color filter by the pigment dispersion method, a radiation-sensitive composition is coated on a glass substrate by a spin coater or a roll coater to form a coated film, which is then pattern exposed and developed to obtain colored pixels. By performing such operation for each color, the color filter can be obtained. As the pigment dispersion method, there is disclosed a negative-type photosensitive composition utilizing a photopolymerizable monomer and a photopolymerization initiator in combination with an alkali-soluble resin (for example, refer to Japanese Patent Application Laid-Open No. H1-102469, Japanese Patent Application Laid-Open No. 1-152499, Japanese Patent Application Laid-Open No. 2-181704, Japanese Patent Application Laid-Open No. 2-199403, Japanese Patent Application Laid-Open No. 4-76062, Japanese Patent Application Laid-Open No. 5-273411, Japanese Patent Application Laid-Open No. 6-184482, and Japanese Patent Application Laid-Open No. 7-140654).
However, recently, a higher definition is desired for color filters for use in solid-state image sensors. However, the conventional pigment dispersion system is incapable of improving the resolution, has a problem of causing an unevenness in color due to coarse pigment particles, and therefore is unsuitable for an application requiring a fine pattern such as a solid-state image sensor. In order to solve this problem, it has been conventionally proposed to use a dye, and a positive-type photosensitive composition using a dye has been disclosed (for example, refer to Japanese Patent Application Laid-Open No. 6-75375, Japanese Patent Application Laid-Open No. 2002-14221, and Japanese Patent Publication (JP-B) No. 7-111485).
However, a colored curable composition containing a dye has the following problems and further improvements are desired.
(1) A dye is generally inferior in heat resistance and light resistance to a pigment, and thus further improvements in the resistances are required.
(2) In a case where a dye has a low molar absorption coefficient, it is required to add a large amount of the dye, and thus other components in the colored curable composition, such as a polymerizable compound, a binder, and a photopolymerization initiator, have to be decreased. Therefore, there are desired improvements in problems such as the decrease in; a curing property of the composition, heat resistance after curing, or developability of an uncured area.
(3) A dye often shows an interaction with other components in the curable composition, and thus it is difficult to regulate the developability (solubility) of a cured area and an uncured area. Therefore, there are also desired improvements in this point.
In this manner, dyes that have been conventionally employed in the photosensitive composition are not satisfactory particularly in the resistance, and, having a low solubility in the photosensitive composition, cannot be easily contained at a high concentration. Therefore, there are desired improvements in these points.
On the other hand, it is known to use a yellow dye in green and red filter arrays of a color filter (for example, refer to Japanese Patent Application Laid-Open No. 2002-14222). However, the yellow dye used for this color filter is insufficient in heat resistance and light resistance. Similarly in a color filter comprising a yellow filter layer, a magenta filter layer, and a cyan filter layer, there is desired a further improvement in resistance in the yellow dye used for the yellow filter layer.
As described above, a dye containing a curable composition is useful in applications requiring a high definition and a uniformity of color such as a solid-state image sensor, however is still incapable of achieving an excellent color hue nor stably maintaining a color concentration and a color hue of the dye, due to fading or the like, and it has been a task to improve resistances such as heat resistance and light resistance in dyes, particularly in yellow dyes. Moreover, it has been one of the tasks to improve the low stability with time of a liquid preparation or a coated film resulting from the low solubility of dyes. Furthermore, it has been also one of the tasks to improve the pattern rectangularity for forming a pattern, and to suppress the situation where films remain in areas other than a desired area for pattern formation (so called “residual film”).